Definition

Chorionic villus sampling is a test that is done during early pregnancy to test for chromosomal abnormalities in the fetus. It involves removing chorionic villi from the placenta. The placenta is the organ that provides nutrients and oxygen to the baby during pregnancy. It also removes waste from the baby’s blood. Chorionic villi is the tissue that makes up most of the placenta. The test is done during the 9th-13th weeks of pregnancy.

Reasons for Test

Chorionic villi contains valuable information about the baby’s genes. By testing chorionic villi, the doctor can find out if the baby has a chromosomal abnormality, like
Down syndrome
. The test can also detect genetic disorders, like
cystic fibrosis
. It cannot detect neural tube defects, such as
spina bifida
.

This test may be considered when:

Other tests, such as a first trimester
ultrasound
or blood tests reveal abnormal results

A prior pregnancy had a chromosomal abnormality

The mother is 35 years old or older

You or your partner is a carrier for a genetic disorder

There is a family history of a genetic disorder

Although a test showing a healthy baby without a genetic disorder is ideal, you will need to be prepared if the results show otherwise. If the test shows that your baby may have a genetic disorder, it may require you to make tough decisions regarding your pregnancy, such as whether or not to continue it. If you do continue with the pregnancy, you will need to address concerns, such as planning for a child with special needs. Your doctor can help you understand the pros and cons of having this test, as well as talk to you about options after you know the results.

What to Expect

Prior to Test

Since you may need to have a full bladder, drink plenty of fluids before the test. However, depending on how your placenta is positioned, you may be asked to urinate before the test. Talk with your doctor about specific ways to prepare for the test. Also, arrange to have someone drive you home from the hospital.

Description of Test

An ultrasound will be used to find out the position of your placenta and your baby’s age. An ultrasound uses sound waves to create images of structures inside the body.

Your abdomen will be cleansed with antiseptic. Using the ultrasound images as a guide, a long, thin needle will be inserted through your abdominal wall. The needle will enter your uterus, avoiding the baby. You may feel cramping at this time. A tissue sample from your placenta will be withdrawn into a syringe through the needle.

After Test

Your baby's heart rate may be monitored using an ultrasound. You will be encouraged to rest when you are home. You will most likely be able to return to normal activities the next day. If you have a RH negative blood type, you will need to receive Rhgam to prevent a condition called isoimmunization.

How Long Will It Take?

30-45 minutes

Will It Hurt?

You may feel some cramping during and after the test. You may also have a small amount of bleeding right after the test.

Results

It may take 1-2 weeks to receive your test results. You will go over your results with your doctor or a genetic counselor.

If the test results are unclear, you may need to have another test called an
amniocentesis
. This is to help get a better understanding of the results.

If the results show that your baby has a genetic disorder or problems with chromosomes, you and your doctor will discuss how to manage your pregnancy. This may be a stressful time. Seeking support from your family, friends, and healthcare team can help.

Call Your Doctor

It is important to monitor your recovery. Alert your doctor to any problems. If any of the following occur, call your doctor:

Heavy bleeding from your vagina

Leaking of amniotic fluid

Uterine contractions

Fever

Chills

If you think you have an emergency, call for emergency medical help right away.

Revision Information

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.